KR20100032685A - Solar cell and method for manufacturing thereof - Google Patents

Abstract

The present invention relates to a solar cell and a method of manufacturing the same. The present invention first forms the second conductive semiconductor layer 102 having the opposite conductivity type on the surface of the semiconductor substrate 100 having the first conductive type. Thereafter, the semiconductor layer formed on the back surface of the semiconductor substrate 100 is formed of the oxide film 104, and the back electrode 108 is formed on the entire surface of the formed oxide film 104. In this case, a portion of the back electrode 108 penetrates through the oxide film 104 to be in contact with the semiconductor substrate 100. Then, a solar cell is manufactured by forming a front electrode 109 in contact with the second conductive semiconductor layer 102. Meanwhile, in the present invention, in addition to the semiconductor layer formed on the rear surface of the semiconductor substrate, the semiconductor layer formed on the side surface may be formed of an oxide film. According to the present invention, the manufacturing process of the solar cell can be simplified to reduce the cost, and the effect of substantially increasing the p-n junction area can be expected, there is an advantage that the efficiency of the solar cell is improved.

Description

Solar cell and method for manufacturing thereof

The present invention relates to a solar cell, and more particularly, to a method of manufacturing a solar cell by oxidizing a part of a semiconductor substrate, and a solar cell produced thereby.

Recently, with increasing interest in environmental problems and energy depletion, there is a growing interest in solar cells as an alternative energy with abundant energy resources, no problems with environmental pollution, and high energy efficiency. The solar cell is an energy conversion device that converts light energy of the sun into electrical energy using a photovoltaic phenomenon.

In order to manufacture the solar cell, a p-n junction must be formed by doping n-type (or p-type) impurities to a p-type (or n-type) substrate. When light is emitted in the p-n junction state, electrons and holes are generated inside, and electrodes are formed on surfaces of the p-type semiconductor and the n-type semiconductor to flow electrons to an external circuit to generate current.

In this case, the edge portion of the semiconductor substrate is doped in the process for forming the p-n junction. This results in the electrical connection between the front electrode and the rear electrode of the solar cell when the entire rear electrode of the solar cell is formed, thereby reducing the efficiency of the solar cell.

Therefore, an edge isolation process for electrically separating the front electrode and the back electrode from each other by removing a doped portion of the semiconductor substrate from the p-n junction of the solar cell is necessarily performed.

1 is a flowchart illustrating a method of manufacturing a solar cell including the edge isolation process as described above.

Referring to FIG. 1, in order to manufacture a solar cell, a cutting and etching process (S10) of cutting a wafer for a solar cell into a required size and then removing surface marks generated during cutting is performed. A texturing process (s12), which is a scratching operation, is performed on the wafer after the etching process. Then, a doping process s14 is performed to diffuse the wafer and other types of impurities to form an emitter in order to make the wafer conductive. After the doping process is completed, performing an etching process (s16) to remove the phosphorus silicate glass (PSG) generated when the emitter is formed, and forming an anti-reflection film to prevent the reflection of sunlight to increase the efficiency (s18) This is done. Next, a metallization process s20 for forming the rear electrode and the front electrode is performed. Finally, an edge isolation process s22 is performed.

Since the doping material is doped to the edge portion of the semiconductor substrate as described above, the edge isolation process is electrically connected to the front electrode and the back electrode of the semiconductor substrate, thereby reducing the efficiency of the semiconductor substrate. It is a process to isolate the front and back electrodes. The edge isolation process may be performed after the doping process. The edge isolation process may be performed by cutting an edge using a laser or a cutting saw after forming the front electrode and the back electrode, etching only the doped edge portion using a photomasking method, or by using a laser or metal scrubber. It is removed by scribing with a driver.

2 illustrates a cross-sectional view of a solar cell in which an edge isolation process is completed in a semiconductor substrate. 2 shows that the emitter layer 32 and the anti-reflection film 34 of the emitter layer 32, the anti-reflection film 34, the back electrode 36, and the front electrode 38 are formed on the semiconductor substrate 30. The edge portion is removed.

However, the solar cell manufacturing method according to the conventional method has the following problems.

First, the edge isolation process was necessary to manufacture a solar cell. In order to perform the edge isolation process, since specific equipment is required separately from laser equipment, cutting saws, and metal scribers according to the process type, the production cost of the solar cell is increased. Similarly, in the case of using an etching process, there is a problem in that the part to be removed is not accurately removed due to the complexity of the process, and there is a problem in that the overall process is complicated.

In the solar cell manufactured by the above method, as shown in FIG. 2, the p-n junction area capable of receiving sunlight is substantially reduced by the portion removed by the edge process. As is well known, the solar cell may be able to make the most of the area of the semiconductor substrate whose raw material is an area capable of receiving sunlight. However, due to the part removed by the edge process, the solar light receiving area is relatively small, and thus the efficiency of the solar cell is inevitably reduced.

Accordingly, an object of the present invention is to solve the above problems, and to simplify the manufacturing process of the solar cell.

Another object of the present invention is to improve the efficiency of a solar cell by not damaging the p-n junction area of the solar cell.

According to a feature of the invention for achieving the above object, a semiconductor substrate having a first conductivity type; A second conductive semiconductor layer having a conductivity type opposite to that of the first conductive type doped on a surface of the semiconductor substrate; At least one front electrode in contact with a portion of the second conductive semiconductor layer; An oxide film formed by oxidizing a portion of the semiconductor layer; The back electrode is formed on the oxide film as a whole, and a part thereof includes a rear electrode formed to contact the semiconductor substrate through the oxide film.

The oxide layer is formed by oxidizing a semiconductor layer positioned on a rear surface of the semiconductor substrate from a semiconductor layer doped with the semiconductor substrate.

The oxide layer is formed by oxidizing a semiconductor layer located on side and rear surfaces of the semiconductor substrate from a semiconductor layer doped with the semiconductor substrate.

The semiconductor substrate may further include an anti-reflection film formed on an upper surface of the semiconductor layer at a position for receiving light.

According to another feature of the invention, the step of forming a semiconductor layer of the second conductive type having the opposite conductivity type on the surface of the semiconductor substrate having the first conductive type; Forming a portion of the semiconductor layer as an oxide film; Forming a rear electrode on the formed oxide film as a whole, while forming a portion of the back electrode to be in contact with the semiconductor substrate through the oxide film; And forming at least one front electrode in contact with a portion of the semiconductor layer.

In the semiconductor layer doped with the semiconductor substrate, an oxide layer is formed by oxidizing the semiconductor layer positioned on the rear surface of the semiconductor substrate.

In the semiconductor layer doped with the semiconductor substrate, an oxide layer is formed by oxidizing the semiconductor layers positioned on the side surfaces and the rear surfaces of the semiconductor substrate.

After the oxide film is formed, the method may further include forming an anti-reflection film on the semiconductor layer at a position for receiving light in the semiconductor layer.

According to another feature of the invention, the oxide film forming step of forming an oxide film by oxidizing the entire surface of the semiconductor substrate having the first conductivity type; An etching step of removing only the oxide film formed on the entire surface of the semiconductor substrate among the formed oxide films; A doping step of doping a semiconductor layer of a second conductive type having a conductivity type opposite to that of the first conductive type of the semiconductor substrate on an entire surface of the semiconductor substrate from which the oxide film is removed; Forming a back electrode on the back oxide film of the semiconductor substrate as a whole, and forming a part of the back electrode to be in contact with the semiconductor substrate through the oxide film; And forming a front electrode to form at least one front electrode in contact with a portion of the semiconductor layer.

After the semiconductor layer is doped, further comprising forming an anti-reflection film on the semiconductor layer.

The front electrode and the rear electrode are electrically separated by the oxide film.

In the present invention, a portion of the semiconductor substrate is oxidized to form an oxide film in a state where the semiconductor substrate is doped with an impurity to form a p-n junction, so that the front electrode and the rear electrode formed on the semiconductor substrate are electrically separated. In this case, the edge isolation process, which is necessary in the conventional solar cell manufacturing process, is omitted, so that the process can be simplified and cost reduction can be expected.

In addition, since the p-n junction of the semiconductor substrate is not removed due to the elimination of the edge isolation process, the p-n junction area is substantially enlarged, and thus the solar light receiving ability of the solar cell is improved.

In addition, the formed oxide film acts as a passivation to reduce the recombination rate of the carrier to improve the efficiency of the solar cell.

Hereinafter, a solar cell manufacturing method according to the present invention will be described in detail with reference to the preferred embodiment shown in the accompanying drawings.

The present invention is to prevent the front electrode and the rear electrode formed on the front and back of the semiconductor substrate to shunt electrically by oxidizing a part of the emitter layer doped to the semiconductor substrate.

3 is a cross-sectional view showing a solar cell manufacturing method according to a first embodiment of the present invention.

First, as shown in FIG. 3A, a second conductive semiconductor layer 102 having a conductivity type opposite to that of the first conductivity type is formed on the semiconductor substrate 100 having the first conductivity type. That is, a p-n junction is formed by doping n-type (or p-type) impurities to a p-type (or n-type) substrate. Since the semiconductor layer 102 serves as an emitter, the following description will be referred to as an emitter layer.

When the pn junction is completed, as shown in FIG. 3B, an oxide layer (hereinafter, referred to as a “back oxide layer”) is oxidized by oxidizing an emitter layer on a rear surface of the semiconductor substrate 100, specifically, a portion of the back electrode 108 to be described below. Will be described). The backside oxide film 104 is not formed on the emitter layer 102 but is formed by oxidizing the emitter layer 102 itself. The backside oxide film 104 is formed by various methods such as thermal oxidation, wet oxidation, and the like. Since the back oxide film 104 formed as described above serves as an insulator and a passivation film, the recombination rate of carriers on the surface of the semiconductor substrate 100 is reduced to improve photoelectric conversion efficiency.

Next, as shown in FIG. 3C, an anti-reflection film 106 is formed on the entire surface of the semiconductor substrate 100, specifically, on the emitter layer where the front electrode 109 to be described below will be formed. .

In the state where the anti-reflection film 106 is formed, the rear electrode 108 and the front electrode (at the front and rear of the semiconductor substrate 100 to generate current by flowing energy of the semiconductor substrate 100 to an external circuit) 109). This state is shown in FIG. 3D. Referring to FIG. 3D, the back electrode 108 penetrates a part of the back oxide film 104 to partially contact the semiconductor substrate 100 in a state where the back electrode 108 is entirely coated on the back oxide film 104. local contact). The front electrode 109 is formed to be in contact with a portion of the emitter layer 102 applied to the entire surface of the semiconductor substrate 100. In the drawing, two front electrodes 109 are formed.

When the solar cell is manufactured as shown in FIG. 3D, the front electrode 109 and the rear electrode 108 remain electrically separated by the rear oxide film 104 serving as an insulator. Therefore, when the circuit is connected to the front electrode 109 and the rear electrode 108, the shunt is prevented. In addition, the back oxide layer 104 also performs a passivation role to reduce the recombination rate of carriers on the surface of the semiconductor substrate 100.

4 is a cross-sectional view showing a solar cell manufacturing method according to a second embodiment of the present invention. In the second embodiment, oxide films are formed on the side surfaces and the rear surfaces of the semiconductor substrate except for the front surface. That is, only the portion where the oxide film is formed is different from the first embodiment, and other processes, that is, the process of forming the emitter layer, the front electrode and the back electrode, and the anti-reflection film, are all performed in the same manner.

This will be described in detail with reference to FIG. 4.

First, as shown in FIG. 4A, a second conductive semiconductor layer 202 having a conductivity type opposite to that of the first conductivity type is formed on the semiconductor substrate 200 having the first conductivity type. That is, a p-n junction is formed by doping n-type (or p-type) impurities to a p-type (or n-type) substrate. Since the semiconductor layer 202 serves as an emitter, the semiconductor layer 202 will be described below as an emitter layer.

When the p-n junction is completed, the oxide layer 204 is formed by oxidizing the emitter layers on the side surfaces and the rear surfaces except for the front surface of the semiconductor substrate 100 as shown in FIG. 4B. At this time, the front surface of the semiconductor substrate 100 is shielded with a hard mask, etc., and the side and the rear surface are oxidized. The oxide film formed on the side is referred to as a side oxide film 204a and the oxide film formed on the back surface is referred to as a back oxide film 204b. The side oxide film 204a and the rear oxide film 204b are formed by oxidizing a part of the emitter layer 202. The side oxide film 204a and the back oxide film 204b are formed by various methods such as thermal oxidation, wet oxidation, and the like. Since the side oxide film 204a and the rear oxide film 204b thus formed serve as an insulator and a passivation film, the recombination rate of carriers on the surface of the semiconductor substrate 200 is reduced to photoelectric conversion. Improve the efficiency.

In FIG. 4C, an antireflection film 206 is formed on the emitter layer 202 on the front surface of the semiconductor substrate 200 to reduce light reflection loss. The anti-reflection film 206 is formed up to the side oxide film 204a.

In the state where the anti-reflection film 206 is formed, the front electrode 209 and the back electrode (on the front and rear of the semiconductor substrate 200 to generate current by flowing energy of the semiconductor substrate 200 to an external circuit) 208). This state is shown in FIG. 4D. Referring to FIG. 4D, the back electrode 208 penetrates a part of the back oxide film 204b to be in contact with the semiconductor substrate 200 in a state where it is entirely coated on the back oxide film 204b. ) Is formed. The front electrode 209 is formed to be in contact with a part of the emitter layer 202 applied to the semiconductor substrate 200. In the drawing, two front electrodes 209 are formed.

When the solar cell in the state as shown in FIG. 4D is manufactured, the front electrode 209 and the rear electrode 208 are electrically separated by the oxide film 204 serving as an insulator. Therefore, when the circuit is connected to the front electrode 109 and the rear electrode 108, the shunt is prevented. The oxide layer 204 also performs a passivation role to reduce the recombination rate of carriers on the surface of the semiconductor substrate.

5 is a cross-sectional view showing a solar cell manufacturing method according to a third embodiment of the present invention. In the third embodiment, after the entire semiconductor substrate is oxidized to form an oxide film, the oxide film formed on the front portion of the semiconductor substrate is removed, and the emitter layer, the front electrode and the back electrode, and the anti-reflection film are formed.

This will be described in detail with reference to FIG. 5.

First, as shown in FIG. 5A, the entire surface of the semiconductor substrate 300 having the first conductivity type is oxidized to form an oxide film 302. This state is shown in FIG. 5B. Referring to FIG. 5B, the oxide film 302 may be divided into a side oxide film 302a, a back oxide film 302b, and a front oxide film 302c.

Then, the front surface oxide film 302c of FIG. 5B is selectively etched to remove the front surface oxide film 302c. This state is shown in Fig. 5C. In FIG. 5C, only the side oxide film 302a and the back oxide film 302b are formed on the semiconductor substrate 300.

Thereafter, in FIG. 5D, a second conductive semiconductor layer 304 having a conductivity type opposite to that of the first conductivity type is formed. Since the semiconductor layer 304 serves as an emitter, the following description will be referred to as an emitter layer.

After the emitter layer 304 is formed, an anti-reflection film 306 is formed on the emitter layer 304 to reduce light reflection loss as shown in FIG. 5E. The antireflection film 306 is formed up to the side oxide film 302a.

In the state where the anti-reflection film 306 is formed, the front electrode 308 and the rear electrode (308) on the front and rear of the semiconductor substrate 300 to generate current by flowing the energy of the semiconductor substrate 300 to an external circuit. 310). This state is shown in FIG. 5F. Referring to FIG. 5F, the rear electrode 310 penetrates a portion of the rear oxide layer 302b so as to contact the semiconductor substrate 300 in a state of being entirely coated on the rear oxide layer 302b. ) Is formed. The front electrode 308 is formed to contact a part of the emitter layer 304 applied to the semiconductor substrate 300. In the drawing, two front electrodes 308 are formed.

When the solar cell is manufactured as shown in FIG. 5F, the front electrode 308 and the rear electrode 310 are electrically separated by the oxide films 302a and 302b serving as an insulator. Therefore, when the circuit is connected to the front electrode 308 and the back electrode 310, the shunt is prevented. In addition, the oxide layers 302a and 302b also serve as passivation to reduce the recombination rate of carriers on the surface of the semiconductor substrate.

As described above, the present embodiment forms a part of the emitter layer doped in the semiconductor substrate as an oxide film, so that the front electrode and the rear electrode are electrically connected to each other even without performing the edge isolation process that is necessarily performed in the conventional solar cell manufacturing process. It can be seen that the state is separated.

The scope of the present invention is not limited to the embodiments described above, but is defined by the claims, and various changes and modifications can be made by those skilled in the art within the scope of the claims. It is self evident.

1 is a flow chart showing a manufacturing method of a typical solar cell.

2 is a cross-sectional view of a solar cell in which an edge isolation process is completed in a general semiconductor substrate.

3 is a cross-sectional view showing a solar cell manufacturing method according to a first embodiment of the present invention.

4 is a cross-sectional view showing a solar cell manufacturing method according to a second embodiment of the present invention.

5 is a sectional view showing a solar cell manufacturing method according to a third embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

100, 200, 300: semiconductor substrate 102, 202, 304: emitter layer

104, 204, 302: oxide film 106, 206, 306: antireflection film

108, 208, 310: rear electrode 109, 209, 308: front electrode

Claims (11)

A semiconductor substrate having a first conductivity type; A second conductive semiconductor layer having a conductivity type opposite to that of the first conductive type doped on a surface of the semiconductor substrate; At least one front electrode in contact with a portion of the second conductive semiconductor layer; An oxide film formed by oxidizing a portion of the semiconductor layer; And, The solar cell of claim 1, wherein the solar cell includes a rear electrode formed on the oxide film to be entirely in contact with the semiconductor substrate through the oxide film. The method of claim 1, The oxide film is a solar cell, characterized in that formed in the semiconductor layer doped in the semiconductor substrate is a semiconductor layer located on the back of the semiconductor substrate is oxidized. The method of claim 1, The oxide film is a solar cell, characterized in that formed in the semiconductor layer doped in the semiconductor substrate is a semiconductor layer located on the side and back of the semiconductor substrate is oxidized. The method of claim 1, And an anti-reflection film formed on an upper surface of the semiconductor layer at a position where light is received from the semiconductor substrate. Doping a semiconductor layer of a second conductive type having an opposite conductivity type to a surface of a semiconductor substrate having a first conductive type; Forming a portion of the semiconductor layer as an oxide film; Forming a rear electrode on the formed oxide film as a whole, while forming a portion of the back electrode to be in contact with the semiconductor substrate through the oxide film; And, Forming at least one front electrode in contact with a portion of the semiconductor layer. The method of claim 5, And forming an oxide film by oxidizing the semiconductor layer positioned on the rear surface of the semiconductor substrate from the semiconductor layer doped to the semiconductor substrate. The method of claim 5, And forming an oxide film by oxidizing the semiconductor layers positioned on side and rear surfaces of the semiconductor substrate doped with the semiconductor substrate. The method according to claim 6 or 7, And forming an anti-reflection film on the semiconductor layer at a position where light is received by the semiconductor layer after the oxide film is formed. Forming an oxide film by oxidizing the entire surface of the semiconductor substrate having the first conductivity type; An etching step of removing only the oxide film formed on the entire surface of the semiconductor substrate among the formed oxide films; A doping step of doping a semiconductor layer of a second conductive type having a conductivity type opposite to that of the first conductive type of the semiconductor substrate on an entire surface of the semiconductor substrate from which the oxide film is removed; Forming a back electrode on the back oxide film of the semiconductor substrate as a whole, and forming a part of the back electrode to be in contact with the semiconductor substrate through the oxide film; And, And a front electrode forming step of forming at least one front electrode in contact with a portion of the semiconductor layer. The method of claim 9, And after the semiconductor layer is doped, forming an anti-reflection film on the semiconductor layer. The method according to claim 5 or 9, The front electrode and the back electrode is a solar cell manufacturing method, characterized in that to maintain the electrically separated state by the oxide film.

Images